1. Field of the Invention
The present invention relates generally to the internal sealing of pipeline joints, and particularly the sealing of inaccessible joints in underground pipelines. Specifically, the present invention relates to an internal seal and method of installation involving a tube shaped, pliable collar member having dovetailed annular locating means defined at opposite ends thereof, and at least two circumferentially recessed portions defined in the collar member and carrying ring shaped cushions of elastic, gumlike material adapted to expand radially in response to expandable tension rings positioned internally of the collar member.
2. Description of the Prior Art
Initial sealing of pipeline joints is conventionally accomplished when the pipeline is laid in individual sections and interfacing joints are sealed by an externally applied seal at the overlapping, adjoining pipe section end portions. However, after prolonged use, it is not unusual for the initially applied seal to develop leaks, thus necessitating resealing of the leaking joints. As will be appreciated, in many instances pipelines are inaccessible for external application of seal. Accordingly, to avoid expensive and inconvenient excavation of pipelines to gain access to the joints which have developed leaks, internal sleeve seals have been developed to facilitate resealing of pipelines internally.
Known internal sleeve seals generally include a tube-like sleeve of an elastic, pliable material which is positioned overlapping the joint, and which is secured in place by ring shaped, radially expandable tension rings which, when expanded, urge the sleeve into sealing relationship against the inner wall of the pipeline at positions adjacent either side of a leaking joint. However, as a result of variations in pipeline roundness, diameter and other tolerance variations, as well as dynamic displacement of the pipeline itself, severe sealing requirements are imposed upon such internal sleeve seals. Known internal sleeve seals conventionally include dovetail like expanding annular spacers protruding from the outer lateral surface thereof, the seals being located at intervals adjacent the tension rings. Thus the seals adjacent the tension rings serve to accommodate variations, either static or dynamic, in the pipeline as a result of the substantial elastic distortion provided by the seal. The stringent requirements of such seals have resulted in high material and manufacturing costs. Further, materials which are particularly adapted to provide an excellent sealing interface with a pipeline generally do not possess sufficient structural strength to adequately seal against migration of, for instance, water from the surrounding environment through the pipeline seal. For this reason, it is often necessary that such known internal sleeve seals be produced with a reinforcing liner to provide sufficient structural strength which is not provided by the highly elastic sleeve sealing material alone.